The atomic force microscope (AFM) is a unique microscope based on a mechanical method which has the following possibilities: (1) It has true atomic resolution, (2) it can measure atomic force (so called atomic force spectroscopy), (3) it can observe even insulator, and (4) it can measure mechanical response. However, contact mode imaging can be rather destructive and can not achieve observation of an atomic defect, although the periodic lattice structure can be imaged. On the other hand, above AFM possibilities may be fulfilled only by noncontact atomic force microscopy (NC-AFM), which demonstrated its possibility at the First and the Second International Workshops on Noncontact Atomic Force Microscopy (NC-AFM98 and 99).
Recently, the noncontact atomic force microscope with true atomic resolution developed into a kind of spectroscopic tool, which can measure three-dimensional force-related map. Here, we will report on site-dependent frequency-shift curves measured on Si(111)7x7 surface using a Si tip which showed a clear difference between those above adatoms and above gaps between adatoms. Next, we will report on distance-dependent NC-AFM image patterns measured on Si(111)r3xr3-Ag surface using a Si tip. Further, we will talk about the possibility that we can control interaction force between tip and sample atoms by placing an adequate atom on the cantilever tip apex. These results show the possibility that the NC-AFM, which utilizes atomic force itself based on the atomic interaction, can provide observation, spectroscopy, discrimination, identification, control and manipulation of individual atomic force and also atom itself. Thus, the NC-AFM will have large possibility as a tool of the coming generation of atomic and molecular nanotechnology and also as the second generation of atom and molecular manipulator, and is expected to develop in very wide fields of science and engineering.
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